CN119063017A - Economizer and pulverized coal industrial boiler system - Google Patents

Abstract

The invention relates to an economizer and a pulverized coal industrial boiler system. The economizer comprises a box body, a heat exchange module, m baffles and a valve, wherein the box body is provided with a flue, a flue gas inlet and a flue gas outlet, the heat exchange module comprises a plurality of heat exchange pipe fittings, the heat exchange pipe fittings are arranged in the flue to form a heat exchange area, the baffles are arranged in the flue, the m baffles divide the heat exchange area and form n sub heat exchange areas, n=m+1, one of the sub heat exchange areas is a main heat exchange area, the m heat exchange areas are auxiliary heat exchange areas, and the valve is arranged at the inlet side of the auxiliary heat exchange areas to control the circulation of flue gas of the auxiliary heat exchange areas. The economizer realizes wide-load denitration of the coal-fired industrial boiler through partition heat exchange, saves the space required by external reconstruction of the economizer, fully utilizes the flow inertia of high-temperature flue gas, economically and effectively adjusts the heat exchange area and the flue gas flow rate according to different operation loads of the boiler, thereby changing the heat quantity and meeting the active reaction temperature requirement of the SCR denitration reactor.

Description

Economizer and pulverized coal industrial boiler system

Technical Field

The invention relates to the technical field of economizers, in particular to an economizer and a pulverized coal industrial boiler system.

Background

Under the current situation that the pulverized coal industrial boiler operates increasingly severely, a higher regulation requirement is provided for the operation load range of the boiler, and under the condition that the industrial boiler is excessively low in load, the flue gas temperature after heat exchange of the economizer, namely the flue gas temperature at the inlet of the SCR denitration reactor, cannot meet the catalyst activity reaction temperature, so that the denitration catalyst activity cannot be wholly or locally maintained in an optimal state, the operation efficiency of the SCR denitration reactor is reduced, the consumption of ammonia water is increased, the ammonia escape rate is increased, and the environmental protection emission requirement cannot be met. When the load of the boiler is large, the temperature of the flue gas after heat exchange of the economizer is high, so that the subsequent bag dust removal flue gas temperature is too high, damage is caused to the bag, the flue gas temperature is too high, heat loss is increased, and even the phenomenon of furnace shutdown occurs.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, the embodiment of the invention provides the economizer, the wide-load denitration of the coal-fired industrial boiler is realized through the zoned heat exchange, the space required by external reconstruction of the economizer is saved, the flow inertia of high-temperature flue gas is fully utilized, the heat exchange area and the flue gas flow rate are economically and effectively adjusted according to different operation loads of the boiler, the heat is changed, and the active reaction temperature requirement of the SCR denitration reactor is met.

The embodiment of the invention provides a pulverized coal industrial boiler system.

The economizer comprises a box body, a heat exchange module, m baffles and a valve, wherein the box body is provided with a flue, a flue gas inlet and a flue gas outlet, the heat exchange module comprises a plurality of heat exchange pipe fittings, the heat exchange pipe fittings are arranged in the flue to form a heat exchange area, the baffles are arranged in the flue, the m baffles divide the heat exchange area and form n sub heat exchange areas, n=m+1, one sub heat exchange area is a main heat exchange area, m heat exchange areas are auxiliary heat exchange areas, and the valve is arranged at the inlet side of the auxiliary heat exchange areas to control the circulation of flue gas of the auxiliary heat exchange areas.

The economizer provided by the embodiment of the invention realizes wide-load denitration of the coal-fired industrial boiler through partition heat exchange, saves the space required by external reconstruction of the economizer, fully utilizes the flow inertia of high-temperature flue gas, and economically and effectively adjusts the heat exchange area and the flue gas flow rate according to different operation loads of the boiler, thereby changing the heat quantity and meeting the active reaction temperature requirement of the SCR denitration reactor.

In some embodiments, the main heat exchange region is located in the middle of the n sub heat exchange regions.

In some embodiments, m is an even number, and m baffles are symmetrically arranged with the central axis of the flue as a center.

In some embodiments, m is 4, and the main heat exchange area occupies 0.45-0.55 of the heat exchange area.

In some embodiments, the m auxiliary heat exchange areas have the same area.

In some embodiments, the distance between the auxiliary heat exchange areas of 0.5m and the corresponding valves is gradually reduced along the direction away from the main heat exchange area.

In some embodiments, adjacent ones of the valves are spaced apart in the direction of extension of the chimney.

In some embodiments, the valve has opening gears of 0%, 20%, 40%, 60%, 80%, and 100%.

In some embodiments, the heat exchange tube has a water inlet and a water outlet, the heat exchange module further comprises a water inlet header and a water outlet header, the water inlet header and the water outlet header are both connected with the tank body, the water inlet is communicated with the water inlet header, and the water outlet is communicated with the water outlet header.

The pulverized coal industrial boiler system of the embodiment of the invention comprises the economizer of any embodiment.

Drawings

FIG. 1 is a schematic diagram of a pulverized coal industrial boiler system according to an embodiment of the present invention;

FIG. 2 is a schematic view of the structure of an economizer according to an embodiment of the present invention;

FIG. 3 is a schematic side view of an economizer of an embodiment of the present invention;

FIG. 4 is a schematic view of a heat exchange tube according to an embodiment of the present invention;

Reference numerals:

the pulverized coal industrial boiler system 1000,

The device comprises an economizer 100, a box body 1, a flue 11, a flue gas inlet 12, a flue gas outlet 13, a heat exchange module 2, heat exchange pipe fittings 21, a water inlet header 22, a water outlet header 23, heat exchange pipes 211, a baffle 3, a valve 4, a main heat exchange area 5, an auxiliary heat exchange area 6, a first auxiliary heat exchange area 61 and a second auxiliary heat exchange area 62.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

As shown in fig. 1, the pulverized coal industrial boiler system 1000 of the embodiment of the invention comprises a boiler, a turning smoke chamber, a high-temperature heating surface, a high Wen Woke, an economizer 100, an SCR denitration reactor, a low-temperature heating surface, a dust removal and desulfurization device and a chimney, wherein high-temperature flue gas in a boiler furnace enters the high Wen Woke for heat exchange through the turning smoke chamber, after heat exchange through the high-temperature heating surface, the flue gas enters the economizer 100 for heat exchange, enters the SCR denitration reactor after heat exchange, and then the high-temperature flue gas after denitration sequentially passes through the low-temperature heating surface, the bag-type dust remover and the dust removal and desulfurization device and is discharged.

As shown in fig. 2 to 4, the economizer 100 according to the embodiment of the present invention includes a case 1, a heat exchange module 2, a baffle 3, and a valve 4. The box 1 is provided with a flue 11, a flue gas inlet 12 and a flue gas outlet 13, wherein the flue gas inlet 12 and the flue gas outlet 13 are respectively the inlet and the outlet of the flue 11. The heat exchange module 2 comprises a plurality of heat exchange pipe fittings 21, and the heat exchange pipe fittings 21 are arranged in the flue 11 to form a heat exchange area. The baffle 3 is arranged in the flue 11, and the baffle 3 is a heat insulation baffle. The baffle 3 is connected with the box 1, and the baffle 3 has m, and m baffles 3 separate the heat transfer region and form n sub heat transfer areas, and n=m+1, and one of them sub heat transfer area is main heat transfer area 5, and m heat transfer areas are auxiliary heat transfer area 6. The valves 4 are arranged at the inlet side of the auxiliary heat exchange area 6 to control the circulation of the flue gas of the auxiliary heat exchange area 6, and the number of the valves 4 is m.

When the high-temperature flue gas passes through the economizer 100, the high-temperature flue gas enters the flue 11 through the flue gas inlet 12, exchanges heat when flowing through the heat exchange pipe fitting 21, and is discharged from the flue gas outlet 13. As shown in fig. 2, the flue gas inlet 12 is located at the lower side of the flue 11, the flue gas outlet 13 is located at the upper side of the flue 11, and the high-temperature flue gas flows from the lower side to the upper side.

When the boiler is in lower operation load, the high-temperature flue gas temperature that the boiler produced is lower, close the valve 4 of the supplementary heat transfer area 6 of economizer 100 for high-temperature flue gas can not flow to supplementary heat transfer area 6, can not exchange heat with the heat transfer pipe fitting 21 of supplementary heat transfer area 6, and high-temperature flue gas is whole to exchange heat through main heat transfer area 5, and the heat transfer area reaches minimumly, and the flue gas velocity of flow reaches maximization simultaneously, thereby heat transfer volume is minimum, and the flue gas temperature reduction that makes the discharge from flue gas export 13 is minimum, and the average flue gas temperature that makes SCR denitration reactor entry can satisfy SCR denitration catalyst's minimum reaction temperature requirement.

When the boiler operation load continues to be lifted, the valve 4 of the auxiliary heat exchange area 6 is opened, and the opening degree and the opening quantity of the valve 4 are gradually increased, so that the circulating area and quantity of the auxiliary heat exchange area 6 are gradually increased, a part of high-temperature flue gas can enter the auxiliary heat exchange area 6, the area of the heat exchange area is gradually increased, the flow rate of the high-temperature flue gas is gradually reduced, the heat exchange quantity is gradually increased, and the flue gas after heat exchange can meet the reaction temperature requirement of the SCR denitration catalyst.

When the boiler is under high operation load, the valves 4 of the auxiliary heat exchange area 6 of the economizer 100 are all opened, high-temperature flue gas flows through the heat exchange pipe fitting 21 of the whole economizer 100, the heat exchange area is maximized, and simultaneously the flue gas flow rate is reduced, and the heat exchange capacity is maximized.

According to the economizer 100 provided by the embodiment of the invention, the heat exchange area is divided into one main heat exchange area 5 and n auxiliary heat exchange areas 6 through m baffles 3, the main heat exchange area 5 is in a circulation state, the valve 4 is arranged at the inlet side of the auxiliary heat exchange area 6, and the circulation of the auxiliary heat exchange area 6 is controlled through controlling the on-off of the valve 4, so that the partition and heat exchange control of the heat exchange areas of the economizer 100 are realized. In addition, the auxiliary heat exchange area 6 and the main heat exchange area 5 belong to the heat exchange area of the economizer 100, the auxiliary heat exchange area 6 is positioned on a high-temperature flue gas flowing path, whether the auxiliary heat exchange area 6 circulates or not changes the flowing direction of the high-temperature flue gas slightly, and the high-temperature flue gas can flow through the auxiliary heat exchange area 6 under the opening state of the valve 4 of the auxiliary heat exchange area 6, so that the heat exchange area and the flue gas flow rate of the economizer 100 can be accurately adjusted by controlling the valve 4 according to different running loads of a boiler, the heat is changed, and the flue gas discharged from the flue gas outlet 13 can reach the active reaction temperature requirement of the SCR denitration reactor. Meanwhile, compared with the valve 4 arranged in the middle or at the outlet side of the auxiliary heat exchange area 6, the valve 4 in the embodiment of the invention can isolate high-temperature flue gas from entering the corresponding auxiliary heat exchange area 6 in the closed state of the valve 4, so that the heat exchange between the high-temperature flue gas and the heat exchange pipe fitting 21 of the auxiliary heat exchange area 6 is avoided, and the problem that the heat exchange regulation control precision is low because the auxiliary heat exchange area 6 is communicated with the main heat exchange area 5 and other circulating auxiliary heat exchange areas 6 through the inlet side, the heat exchange pipe fitting 21 which does not participate in heat exchange exchanges heat and the gas after heat exchange enters other circulating heat exchange areas (the main heat exchange area 5 and other circulating auxiliary heat exchange areas 6) along with the main airflow of the high-temperature flue gas is avoided.

Compared with the prior art that the flue gas bypass, the water bypass or the classified economizer is adopted for adjustment, the economizer 100 provided by the embodiment of the invention not only can fully utilize the inertia of high-temperature flue gas flow and ensure the drainage effect of the auxiliary heat exchange area 6 on the high-temperature flue gas, but also can utilize the existing equipment space on the basis of the existing boiler economizer to reform the economizer to form the economizer provided by the invention, and has low reforming difficulty and low cost.

Therefore, the economizer 100 of the embodiment of the invention realizes wide-load denitration of the coal-fired industrial boiler through zoned heat exchange, saves the space required by external reconstruction of the economizer 100, fully utilizes the flow inertia of high-temperature flue gas, and economically and effectively adjusts the heat exchange area and the flue gas flow rate according to different running loads of the boiler, thereby changing the heat quantity and meeting the active reaction temperature requirement of the SCR denitration reactor.

Specifically, the heat exchange pipe fitting 21 is provided with a water inlet and a water outlet, the heat exchange module 2 further comprises a water inlet header 22 and a water outlet header 23, the water inlet header 22 and the water outlet header 23 are both connected with the tank body 1, the water inlet is communicated with the water inlet header 22, and the water outlet is communicated with the water outlet header 23. The water inlet header 22 is communicated with a water pipeline of the low-temperature heating surface, and the water outlet header 23 is communicated with a pipeline of the high-temperature heating surface.

In some embodiments, the main heat exchange area 5 is located in the middle of the n sub heat exchange areas, and then the auxiliary heat exchange areas 6 are distributed on two sides of the main heat exchange area 5. For ease of description, the auxiliary heat transfer zones 6 are ordered in a direction gradually away from the main heat transfer zone 5, i.e. a first auxiliary heat transfer zone 61 adjacent to the main heat transfer zone 5, a second auxiliary heat transfer zone 62 adjacent to the first auxiliary heat transfer zone 61, etc. During the stepwise increasing of the number of openings of the valves 4 of the economizer 100, the valves of the first auxiliary heat exchanger zone 61 are opened one by one, i.e. the second auxiliary heat exchanger zone 62 is opened first. The main heat exchange area 5 is positioned in the middle of the n sub heat exchange areas, so that the distance between the auxiliary heat exchange areas 6 and the main heat exchange area 5 is reduced, the change path of flowing high-temperature flue gas can be reduced in the process of adjusting the circulation or closing of the auxiliary heat exchange areas 6, the high-temperature flue gas is ensured to flow according to the set change path, the accuracy of adjusting the heat exchange area and the flue gas flow rate of the economizer 100 is ensured, the accuracy of adjusting the heat exchange amount is ensured, and the requirement of the SCR denitration reactor on the active reaction temperature is further met.

In some embodiments, m is an even number, m is greater than or equal to 2, and m baffles 3 are symmetrically arranged with the central axis of the flue 11 as a center, so that 0.5m auxiliary heat exchange areas 6 are distributed on two sides of the main heat exchange area 5, and the auxiliary heat exchange areas 6 on two sides are symmetrical relative to the main heat exchange area 5. For example, two first auxiliary heat exchange areas 61 are symmetrical with respect to the main heat exchange area 5, and two second auxiliary heat exchange areas 62 are symmetrical with respect to the main heat exchange area 5. When the valves 4 of the two first auxiliary heat exchange areas 61 are opened simultaneously, the two first auxiliary heat exchange areas 61 are symmetrical with respect to the main heat exchange area 5, so that the flow rates of the flue gas entering the two first auxiliary heat exchange areas 61 are similar, the heat exchange amounts are similar, and the temperatures of the two sides of the flue gas after heat exchange (i.e. the flue gas after heat exchange of the two auxiliary heat exchange areas 61) are similar. Therefore, the m baffles 3 are symmetrically arranged by taking the central axis of the flue 11 as the center, so that the uniformity of the distribution of the high-temperature flue gas in the auxiliary heat exchange areas 6 on the two sides of the main heat exchange area 5 is facilitated, the temperature difference of different areas of the flue gas after heat exchange is reduced, the uniformity of the flue gas temperature distribution of the flue gas entering the SCR denitration reactor is ensured, and the normal operation of the SCR denitration reactor is further ensured.

In some embodiments, the m auxiliary heat exchange areas 6 are the same area. Under the condition that the auxiliary heat exchange areas 6 participate in heat exchange, the areas of the auxiliary heat exchange areas 6 are the same, so that the uniformity of distribution of high-temperature flue gas on the two sides of the main heat exchange area 5 is improved, the temperature difference of different areas of the flue gas after heat exchange is reduced, the uniformity of the flue gas temperature distribution of the flue gas entering the SCR denitration reactor is further ensured, and the normal operation of the SCR denitration reactor is further ensured.

In some embodiments, the distance between the 0.5m auxiliary heat exchange areas 6 and the corresponding valves 4 gradually decreases in a direction away from the main heat exchange area 5. I.e. the distance between the first auxiliary heat transfer area 61 and the corresponding valve 4 is the largest and the distance between the edge auxiliary heat transfer area 6 and the opposite valve 4 is the smallest, i.e. the valve 4 of the edge auxiliary heat transfer area 6 is the highest. The edge of the flue 11 is a serious area where the flue 11 is flushed and abraded by the flue, and the economizer 100 of the embodiment of the invention has the highest position of the valve 4 at the edge of the flue 11, can buffer delay of high-speed flow, and weakens flushing and abrasion of the flue to buffer the high-speed flue.

In some embodiments, adjacent valves 4 are spaced apart in the direction of extension of flue 11, which can provide space for operation or control of valves 4, facilitating personnel control of the opening and closing of valves 4.

Specifically, the valve 4 is a manual valve 4. The valve 4 is made of 450 ℃ resistant stainless steel.

The valve 4 has opening gear positions of 0%, 20%, 40%, 60%, 80% and 100%. When the valve 4 is in the opening gear of 0%, the valve 4 is in a closed state. When the valve 4 is in the 100% opening gear, the valve 4 is in the full open state.

Specifically, if m is 4, the number of auxiliary heat exchange areas 6 is 4, and two first auxiliary heat exchange areas 61 and two second auxiliary heat exchange areas 62 are respectively used. The main heat exchange area 5 occupies 0.45-0.55 of the heat exchange area.

In this embodiment, the heat exchange tube 21 includes 3 heat exchange tubes 211 with a diameter of 45mm, and the number of heat exchange tubes 21 is 80. The water inlet header 22 and the water outlet header 23 are 18 water headers with diameters of 377mm in parallel. The water from the low temperature heating surface of the boiler enters the heat exchange module 2 from the water inlet header 22, flows out from the water outlet header 23 after fully exchanging heat through the heat exchange pipe of the economizer 100, is introduced into the high temperature heating surface of the boiler through the connecting pipe, and has the rated circulating water quantity 1147t/h and the rated working pressure of 1.7MPa.

In the use state of the economizer 100 according to the embodiment of the present invention, the specific adjustment operation process is as follows.

When the boiler is in lower operation load, namely 40% -50% of full load, the valves 4 of the auxiliary heat exchange area 6 of the economizer 100 are all closed, the heat exchange area of the economizer 100 is the main heat exchange area 5, high-temperature flue gas is subjected to heat exchange through the main heat exchange area 5, the heat exchange area is minimum, the flue gas flow rate is maximum, the heat exchange amount is minimum, the average flue gas temperature at the inlet of the SCR denitration reactor is more than 310 ℃, and the minimum reaction temperature requirement of the SCR denitration catalyst is met.

When the boiler operation load continues to rise, the opening degree of the valve 4 of the first auxiliary heat exchange area 61 is controlled to be gradually adjusted from 0% to 100%, until the boiler load reaches 70% of full load, the valve 4 of the first auxiliary heat exchange area 61 is fully opened, and the average smoke temperature at the inlet of the SCR denitration reactor is about 350 ℃.

When the boiler operation load is continuously increased from 70%, the valve 4 of the first auxiliary heat exchange area 61 is kept fully opened, the opening of the valve 4 of the second auxiliary heat exchange area 62 is adjusted to gradually change from 0% to 100%, and the average smoke temperature at the inlet of the SCR denitration reactor is between 350 ℃ and 380 ℃ during the period, so that the optimal reaction temperature range of the SCR denitration catalyst is reached.

When the boiler is at high operation load, namely more than 90% of full load, the valves 4 of the auxiliary heat exchange area 6 of the economizer 100 are all opened, high-temperature flue gas flows through the whole economizer 100, the heat exchange area is maximum, the flue gas flow rate is reduced, the heat exchange capacity is maximum, and the average flue gas temperature at the inlet of the SCR denitration reactor is not more than 420 ℃.

The economizer 100 of the embodiment of the invention partitions the heat exchange area to form different heat exchange areas, realizes partitioned heat exchange, fully utilizes the inertia of high-temperature flue gas without greatly increasing the resistance of high-temperature flue gas, economically and effectively solves the problem that the flue gas temperature at the inlet of the SCR denitration reactor cannot meet the catalytic reaction temperature due to different loads and coal types in the operation of an industrial boiler, has the advantages of simple modification, simple and convenient adjustment, stable operation, good effect, saving the heat exchange space of a boiler system and the like, can realize the stable long-time operation of the pulverized coal industrial boiler within the operation load range of 40% -100%, and provides a new way for solving the design and engineering application of the wide-load denitration economizer 100 of the pulverized coal industrial boiler.

After the economizer 100 provided by the embodiment of the invention is applied, the operation load range of the boiler is increased by 27.5%, the total operation time of the boiler in a heating season is increased by 59.69%, the total operation time of the boiler in a full load reaches 52.52% of the whole heating season, the heat supply of the boiler is increased by 82.65%, the phenomenon that the flue gas inlet temperature of the SCR denitration reactor is too high or too low does not occur in the whole heating season, the operation fault is reduced, the stable long-time operation of the boiler under a wide load is ensured, the overhaul workload of workers is reduced, and the manpower and material resources are saved.

The economizer 100 of the embodiment of the invention can be further popularized to the field of deep flexible peak regulation and denitration of the coal-fired generator set of the power station boiler.

In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed, mechanically connected, electrically connected, or communicable with each other, directly connected, indirectly connected through an intervening medium, or in communication between two elements or in an interactive relationship between two elements, unless otherwise explicitly specified. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present invention, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

For purposes of this disclosure, the terms "one embodiment," "some embodiments," "example," "a particular example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims (10)

1. A coal economizer (100), characterized by comprising: A box body (1), wherein the box body (1) has a flue (11), a smoke inlet (12) and a smoke outlet (13); A heat exchange module (2), the heat exchange module (2) comprising a plurality of heat exchange pipes (21), the heat exchange pipes (21) being arranged in the flue (11) to form a heat exchange area; m baffles (3), the baffles (3) being arranged in the flue (11), the m baffles (3) dividing the heat exchange area and forming n sub-heat exchange areas, n=m+1, one of the sub-heat exchange areas being a main heat exchange area (5), and the m heat exchange areas being auxiliary heat exchange areas (6); A valve (4), wherein the valve (4) is arranged at the inlet side of the auxiliary heat exchange zone (6) to control the flow of flue gas in the auxiliary heat exchange zone (6). 2. The economizer (100) according to claim 1 is characterized in that the main heat exchange zone (5) is located in the middle of the n sub-heat exchange zones. 3. The economizer (100) according to claim 2 is characterized in that m is an even number, and the m baffles (3) are symmetrically arranged with the central axis of the flue (11) as the center. 4. The economizer (100) according to claim 3, characterized in that m is 4, and the main heat exchange zone (5) occupies 0.45-0.55 of the heat exchange area. 5. The economizer (100) according to claim 3, characterized in that the areas of the m auxiliary heat exchange zones (6) are the same. 6. The economizer (100) according to claim 2 is characterized in that, along the direction away from the main heat exchange zone (5), the distance between the 0.5m auxiliary heat exchange zone (6) and the corresponding valve (4) gradually decreases. 7. The economizer (100) according to claim 6, characterized in that adjacent valves (4) are spaced apart in the extension direction of the flue (11). 8. The economizer (100) according to claim 1, characterized in that the valve (4) has opening positions of 0%, 20%, 40%, 60%, 80% and 100%. 9. The economizer (100) according to claim 1 is characterized in that the heat exchange pipe (21) has a water inlet and a water outlet, and the heat exchange module (2) further includes a water inlet header (22) and a water outlet header (23), the water inlet header (22) and the water outlet header (23) are both connected to the box body (1), the water inlet is connected to the water inlet header (22), and the water outlet is connected to the water outlet header (23). 10. A pulverized coal industrial boiler system (1000), characterized by comprising the economizer (100) according to any one of claims 1 to 9.